On Fri, Apr 03, 2015 at 12:25:14PM +0800, Xiao Guangrong wrote: > > >On 03/30/2015 07:48 AM, Wanpeng Li wrote: >>There are two scenarios for the requirement of collapsing small sptes >>into large sptes. >>- dirty logging tracks sptes in 4k granularity, so large sptes are splitted, >> the large sptes will be reallocated in the destination machine and the >> guest in the source machine will be destroyed when live migration >> successfully. >> However, the guest in the source machine will continue to run if live >> migration >> fail due to some reasons, the sptes still keep small which lead to bad >> performance. >>- our customers write tools to track the dirty speed of guests by EPT D >>bit/PML >> in order to determine the most appropriate one to be live migrated, however >> sptes will still keep small after tracking dirty speed. >> >>This patch introduce lazy collapse small sptes into large sptes, the memory >>region >>will be scanned on the ioctl context when dirty log is stopped, the ones >>which can >>be collapsed into large pages will be dropped during the scan, it depends the >>on >>later #PF to reallocate all large sptes. >> >>Signed-off-by: Wanpeng Li <[email protected]> >>--- >> arch/x86/include/asm/kvm_host.h | 2 ++ >> arch/x86/kvm/mmu.c | 66 >> +++++++++++++++++++++++++++++++++++++++++ >> arch/x86/kvm/x86.c | 5 ++++ >> 3 files changed, 73 insertions(+) >> >>diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >>index a236e39..73de5d3 100644 >>--- a/arch/x86/include/asm/kvm_host.h >>+++ b/arch/x86/include/asm/kvm_host.h >>@@ -859,6 +859,8 @@ void kvm_mmu_set_mask_ptes(u64 user_mask, u64 >>accessed_mask, >> void kvm_mmu_reset_context(struct kvm_vcpu *vcpu); >> void kvm_mmu_slot_remove_write_access(struct kvm *kvm, >> struct kvm_memory_slot *memslot); >>+void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, >>+ struct kvm_memory_slot *memslot); >> void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm, >> struct kvm_memory_slot *memslot); >> void kvm_mmu_slot_largepage_remove_write_access(struct kvm *kvm, >>diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c >>index cee7592..d25ced1 100644 >>--- a/arch/x86/kvm/mmu.c >>+++ b/arch/x86/kvm/mmu.c >>@@ -4465,6 +4465,72 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, >> kvm_flush_remote_tlbs(kvm); >> } >> >>+static int kvm_mmu_zap_collapsible_spte(struct kvm *kvm, >>+ unsigned long *rmapp) > >Can use 'bool' instead of 'int'. You used 'bool' in >kvm_mmu_zap_collapsible_sptes anyway. > >>+{ >>+ u64 *sptep; >>+ struct rmap_iterator iter; >>+ int need_tlb_flush = 0; >>+ pfn_t pfn; >>+ struct kvm_mmu_page *sp; >>+ >>+ for (sptep = rmap_get_first(*rmapp, &iter); sptep;) { >>+ BUG_ON(!(*sptep & PT_PRESENT_MASK)); >>+ >>+ sp = page_header(__pa(sptep)); >>+ pfn = spte_to_pfn(*sptep); >>+ if (sp->role.direct && > >It only works on direct mapping, please drop a comment to explain >why. > >>+ !kvm_is_reserved_pfn(pfn) && >>+ PageTransCompound(pfn_to_page(pfn))) { >>+ drop_spte(kvm, sptep); >>+ need_tlb_flush = 1; >>+ } >>+ sptep = rmap_get_next(&iter); > >You can not get the next spte after drop the current spte. Please >refer to kvm_unmap_rmapp(). > >>+ } >>+ >>+ return need_tlb_flush; >>+} >>+ >>+void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, >>+ struct kvm_memory_slot *memslot) >>+{ >>+ bool flush = false; >>+ unsigned long *rmapp; >>+ unsigned long last_index, index; >>+ gfn_t gfn_start, gfn_end; >>+ >>+ spin_lock(&kvm->mmu_lock); >>+ >>+ gfn_start = memslot->base_gfn; >>+ gfn_end = memslot->base_gfn + memslot->npages - 1; >>+ >>+ if (gfn_start >= gfn_end) >>+ goto out; >>+ >>+ rmapp = memslot->arch.rmap[0]; >>+ last_index = gfn_to_index(gfn_end, memslot->base_gfn, >>+ PT_PAGE_TABLE_LEVEL); >>+ >>+ for (index = 0; index <= last_index; ++index, ++rmapp) { >>+ if (*rmapp) >>+ flush |= kvm_mmu_zap_collapsible_spte(kvm, rmapp); >>+ >>+ if (need_resched() || spin_needbreak(&kvm->mmu_lock)) { >>+ if (flush) { >>+ kvm_flush_remote_tlbs(kvm); >>+ flush = false; >>+ } >>+ cond_resched_lock(&kvm->mmu_lock); >>+ } >>+ } >>+ >>+ if (flush) >>+ kvm_flush_remote_tlbs(kvm); >>+ >>+out: >>+ spin_unlock(&kvm->mmu_lock); >>+} >>+ >> void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm, >> struct kvm_memory_slot *memslot) >> { >>diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >>index c5f7e03..6037389 100644 >>--- a/arch/x86/kvm/x86.c >>+++ b/arch/x86/kvm/x86.c >>@@ -7618,6 +7618,11 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, >> /* It's OK to get 'new' slot here as it has already been installed */ >> new = id_to_memslot(kvm->memslots, mem->slot); >> >>+ if ((change != KVM_MR_DELETE) && >>+ (old->flags & KVM_MEM_LOG_DIRTY_PAGES) && >>+ !(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) >>+ kvm_mmu_zap_collapsible_sptes(kvm, new); >>+ > >You'd better drop comments here to explain the situation.
Just handle all your comments in v2, thanks for your review. ;) Regards, Wanpeng Li -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
